Hydrocarbonoxy-containing silicone fluids useful as hydraulic fluids

ABSTRACT

A silicone polymer fluid useful as a brake fluid comprising a polymer or monomer having 0 to 100 mole percent of polymeric or monomeric units selected from  P 2  Si(OM) 2  units, ##EQU1## units and R 2  SiO units. 0 to 100 mole percent of polymeric and monomeric units selected from  RSi(OM) 3  units. 
     Units. ##EQU2## units, ##EQU3## units, and RSiO 3/2  units. 0 to 10 mole percent of units selected from the class consisting of (MO) 3  SiO 1/2  units. (MO) 2  SiO units. (MO)SiO 3/2  units and SiO 2  units and 0 to 5 mole percent of units selected from R 3  SiO 1/2  units wherein the viscosity of the polymer may vary from 2 to 400 centistones at 25°C. R is a monovalent hydrocarbon radical, M is selected from alkyl, alkoxy, alkylene, alkoxyalkyleneoxyalkylene and alkyl polyether substituent radicals, wherein the preferred substituent for M is 2-methoxy-2-ethoxy-ethylene or higher and R is preferably methyl.

This application is a division of copending application Ser. No.256,483, now U.S. Pat. No. 3,821,114, filed May 24, 1972.

BACKGROUND OF THE INVENTION

The present invention relates to silicone polymer fluids that are usefulas hydraulic fluids and more particularly the present invention relatesto silicone polymer fluids where a substantial portion of thesubstituent groups on the silicon atoms are alkoxy groups and variousother types of alcoholic substituent groups which groups are attached tothe silicon atoms.

Most brake fluids that are presently sold are basically glycol basedpolyethers which vary from case to case depending on the type ofpolyether units and the number of polyether units in the polymer chain.Although such brake fluids have found wide acceptance and usage invehicles and particularly automobiles, such glycol base fluids havevarious disadvantages so that various automobile manufacturers havesought to obtain a better quality of brake fluid so that such brakefluid when inserted into the brake system of an automobile would providea higher factor of safety.

One of the disadvantages of such glycol based polyether brake fluids isthat it has a rather limited high temperature stability. Thus, it hasbeen found that at some temperatures to which the brake system of anautomobile may conceivably be exposed to, the brake fluids presently onthe market might degrade or evaporate. It has also been found that atsuch high temperatures which the brake system of an automobile might beexposed to that the brake fluids presently on the market might possiblyvaporize, causing spontaneous brake failure. Thus, the brake fluidspresently on the market tend to have an undesirable low boiling point.

Another disadvantage of the glycol based polyether brake fluidspresently on the market is that they are hygroscopic, that is, suchfluids tend to pick up water and moisture from the air quite easily.Although such glycol based polyether brake fluids have the property ofbeing compatible with large amounts of water, nevertheless, due to theirhygroscopicity they will over a period of time absorb a large amount ofmoisture into the system, such that when the compatibility level of thewater in the polyether glycol based fluid is exceeded the water willcause undesirable changes in the physical properties of the brake fluid.At low temperatures such large amounts of absorbed water in thepolyether glycol based brake fluid will undesirably increase theviscosity of the brake fluid and deleteriously affect the performance ofthe brakes. At high temperatures the presence of large amounts of watermay result in the water being vaporized to create what is known asvapor-lock in the hydraulic lines of the brake system, which alsoresults in improper performance of the brakes.

To meet these disadvantages of the brake fluids presently on the market,manufacturers have looked at other types of fluids that would have ahigher performance factor in automobile brake systems and particularlyhave looked on brake fluids that would not have the disadvantages of theglycol based polyether brake fluids which are mentioned above.

Several silicone fluids have been proposed for use as brake fluids.Silicone fluids have the particular advantage of a very high flash pointand do not degrade and thus retain their chemical stability at hightemperatures. In addition, silicone fluids have a high fire point suchthat even during periods of exceptional stress in the operation of thebrake hydraulic system of an automobile the temperature that is reachedin the hydraulic system is considerably below the flash point and firepoint of such silicone fluids. In addition, silicone fluids have theadditional advantage that they have a desirably low viscosity at lowtemperatures even at temperatures as low as -40°C. In addition, mostsilicone fluids are not hygroscopic such that they take up very littlewater or moisture from the air and thus are not usually bothered withthe problems of excessive water pick-up. However, it has been envisionedthat water by some means or other may by accident enter into thehydraulic system so that it is desirable that a silicone fluid becompatible with a reasonable amount of water, that is, the water can beabsorbed into the silicone fluid. In addition, it is desirable to obtaina silicone fluid which has as low viscosity as possible at a lowtemperature, say, of -40°C and yet have a minimum viscosity at highoperable temperatures.

The necessity for such a desirably low viscosity of the brake fluid atlow temperatures, say, as -40°C is so that such a fluid can be used invery cold climates and even in artic regions. It should be pointed outthat in artic areas because of the large amount of precipitation andparticularly snow, it is desirable that the silicone brake fluid becompatible with a certain amount of water, say, up to 6% by weight ofwater.

In addition, it is desired that the silicone fluid that is to be used asa brake fluid be compatible with the common brake fluids presently onthe market, that is, the non-silicone brake fluids, the glycol basedpolyether fluids. Thus, if by accident some non-silicone brake fluidenters the system or if silicone fluid is added by accident to ahydraulic braking system to replace some glycol based polyether fluid,then it is desirable that the silicone fluid be compatible with theglycol based polyether fluid.

While the above discussion has been directed to the use of a siliconepolymer as a brake fluid, it should be mentioned that the above desiredproperties for a silicone fluid, that is, a silicone fluid having theabove-named advantages over glycol based polyether fluids, would be asuperior hydraulic fluid for use in hydraulic systems. Thus, such ahydraulic system may or may not include a hydraulic reservoir; it wouldinclude a mechanical hydraulic activating means which may for instancebe a brake pedal to which mechanical pressure is applied; and it wouldalso include a hydraulic activated means which may be the pistons orother types of mechanisms that are activated by the hydraulic pressurein the brake drum shoe or disc brake or other type of hydraulic systemassembly. The hydraulic activating means, hydraulic activated means andhydraulic reservoir are all connected by the necessary hydraulic lines.Thus, it is not intended to limit the application of the novel siliconepolymer fluid disclosed in this application solely for use in brakehydraulic systems but such a fluid may be used in all types of knownhydraulic systems which fluid would have the superior advantages andproperties of silicone fluids as well as the specific advantagesmentioned above.

Accordingly, it is one object of the present invention to provide fornovel silicone polymer fluid having a viscosity that may vary from 2 to400 centistokes and having a substantial amount of hydrocarbonoxysubstituents and hydrocarbonoxy-type substituents on the silicon atoms.

It is another object of the present invention to provide for a novelprocess for producing a silicone polymer fluid having a viscosity from 2to 400 centistokes and having a substantial amount of hydrocarbonoxy andhydrocarbonoxy-type substituents of the silicon atom.

It is yet an additonal object of the present invention to provide anovel silicone polymer fluid useful as a hydraulic fluid andparticularly useful as a hydraulic brake fluid.

It is an additional object of the present invention to provide for anovel silicone polymer fluid having a viscosity of 2 to 400 centistokesat 25°C and which has a compatibility of up to 100% by weight of thefluid of water.

It is still an additional object of the present invention to provide anovel silicone polymer fluid which may be used as a hydraulic fluid andis generally compatible with brake fluids presently sold in commerce.

These and other objects of the present invention are accomplished bymeans of the invention defined below.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a novelsilicone polymer fluid useful as a brake fluid comprising a polymerhaving 0 to 100 mole percent of monomeric units and polymeric unitsselected from R₂ Si(MO).sub. 2 units, ##STR1## units and R₂ SiO unitsand mixtures thereof, 0 to 100 mole percent of units selected frommonomeric units and polymeric units, RSi(OM).sub. 3 units, ##STR2##units, ##STR3## units, and RSiO.sub. 3/2 units and mixtures thereof, 0to 10 mole percent of polymeric units selected from (MO)₃ SiO.sub. 1/2units, (MO)₂ SiO units, MO SiO_(3/2) units and SiO.sub. 2 units andmixtures thereof, and 0 to 5 percent of polymeric units selected from R₃SiO.sub. 1/2 units, wherein any class all of the different units may bepresent in any combination or mixture and wherein all or some of theunits in each class may be present and are normally presented in alltype of combinations with the units of the other classes within the molepercent limits set forth above; where the molar amount of MO groupspresent based on the total of moles of R and MO groups present togethermay vary from 0 to 95 mole percent and in which the viscosity of thepolymer may vary from 2 to 400 centistokes at 25°C, R is selected fromthe class consisting of monovalent hydrocarbon radicals, halogenatedmonovalent hydrocarbon radicals and cyanoalkyl radicals, M is selectedfrom the class consisting of R--, ROR'--, ROR'OR'--, R(OC_(x)H_(2x))_(n) --, and ##STR4## such that R is as previously defined andthe various R radicals attached to the silicon atoms may be the same orall different and the various R radicals present in the M groups may bethe same as the R radicals attached to the silicon atoms or different;where the R' radical is selected from the class consisting of divalenthydrocarbon radicals and halogenated divalent hydrocarbon radicals andwhere the various R' radicals may be the same or different and whereinR' preferably represents a divalent saturated aliphatic radical of 2 to10 carbon atoms; x in the polyether group defined above varies from 2 to4 and n is at least 4 and may be as high as 100. The preferred radicalfor M is 2-methoxy-2-ethoxy ethylene and higher and the R group attachedto the silicon is preferably methyl. In most cases, the hydrocarbonoxyfluid is a polymer. However, it can also be a monomer, a mixture ofmonomers or a mixture of monomers with polymers within the scope of theabove formula. The monomers that may be present are, of course, R₂Si(OM).sub. 2 and RSi(OM).sub. 3.

When the above novel silicone fluid is used as a silicone brake fluid inautomobiles to obtain the optimum compatibility between this novelsilicone fluid and the non-silicone fluids presently sold in commerce,it is preferred that the fluid polymer of the present invention have 20%by weight to 48% by weight of MO groups based on the total weight of thefluid.

More preferably, the novel silicone hydraulic fluid of the presentinvention which may be used as a brake fluid contains 75 to 95 molepercent of polymeric units selected from ##STR5## units and R₂ SiO unitsin combination with 5 to 25 mole percent of units selected from theclass consisting of ##STR6## units, ##STR7## units, and RSiO.sub. 3/2units with trace amounts of the other units. Thus, in the preferredembodiment of the novel silicone fluid of the present invention there ispreferably only trace amounts of (MO)₃ SiO.sub. 1/2 units, (MO)₂ SiOunits, MO SiO.sub. 3/2 units and SiO.sub. 2 units and there ispreferably only trace amounts of R₃ SiO.sub. 1/2 units. It is found thata brake fluid with only the preferred units discussed above has the morepreferred properties and in addition is produced more economically.However, the other types of units mentioned previously may also bepresent in the silicone polymer fluid of the present invention in theamounts indicated previously depending on the type of starting materialsthat are used and the amounts of the starting materials that are used toprepare the novel silicone polymers of the present case.

The above silicone fluid mixture, irrespective of its form, has beenfound to be especially suitable for use as a brake fluid. However, it isnot intended to limit the application in the present specification ofthe silicone fluid mixture defined above to use just in the hydraulicsystem of an automobile or other type of vehicle. More broadly, thesilicone fluid mixture of the present invention is directed to asuitable use as a hydraulic fluid in any hydraulic system. In the morespecific preferred embodiment of the present invention the siliconefluid mixture defined above, with or without the various additives, isparticularly suitable for use in the hydraulic brake system of anautomobile, truck or other such type of vehicle. Such an automotivevehicle will contain as part of its brake system a hydraulic reservoir,a brake drum cylinder with the necessary pistons therein or thecomparable equipment to be found in a disc brake system and in addition,the necessary pistons and connecting links by which the operator of thevehicle applies mechanical pressure which is transferred into hydraulicpressure. The reservoir, brake drum, cylinder, pistons, as well as theequivalent disc brake appendages and the mechanical force applyingequipment are all connected by the necessary hydraulic lines and othertypes of supplementary equipment.

To generally describe such a hydraulic brake system, in all types ofvehicles irrespective of the type of vehicle, reference will simply bemade to a hydraulic reservoir; to the hydraulic activating means whichis the mechanical means by which an operator of a vehicle translates hisphysical pressure, that is, the brake pedal and the piston which itactivates; to hydraulic activated means which will refer to the brakedrum cylinder and the pistons therein or the equivalent disc brakesystem; and to hydraulic lines, that is, the hydraulic lines, connectingall of these parts of the hydraulic brake system together. Since thepurpose of the present application is not to define or describe a noveltype of brake system or a novel type of hydraulic system per se, thedifferent types of brake systems and hydraulic systems will not bedescribed herein in detail since the direction of the presentapplication is to describe a novel hydraulic fluid and, more preferably,a novel hydraulic fluid as used in a hydraulic brake system.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The radical R appearing in the above formulas is well known in the art;is typlified by the radicals usually associated with silicon bondedorganic groups in the case of R; and generally associated with divalenthydrocarbon radicals in the case of R'. The organic radicals representedby R include monovalent hydrocarbon radicals, halogenated monovalenthydrocarbon radicals and cyanoalkyl radicals. Thus, the radical R may bealkyl, such as methyl, ethyl, propyl, butyl, octyl; aryl radicals, suchas phenyl, tolyl, xylyl, naphthyl radicals; aralkyl radicals, such as,benxyl, phenylethyl radicals; olefinically unsaturated monovalenthydrocarbon radicals, such as vinyl, allyl, cyclohexyl radicals;cycloalkyl radicals, such as cyclohexyl, cyclopheptyl, etc.; halogenatedmonovalent hydrocarbon radicals, such as chloromethyl, dichloropropyl,1,1-trifluoropropyl, chlorophenyl, dibromophenyl and other suchradicals; cyanoalkyl radicals, such as cyanoethyl, cyanopropyl, etc. Thevarious R radicals attached to the silicon atom may be the same ofdifferent. Thus, all the R radicals attached to the silicon atom may belower alkyl, that is, lower alkyl radicals, having 1 to 8 carbon atomsor a mixture of various types of lower alkyl radicals or a mixture oflower alkyl radicals with the other types of radicals defined above forthe R group. Preferably, the R radicals attached to the silicon atomsare selected from lower alkyl radicals having 1 to 8 carbon atoms andmore preferably, methyl. The R radicals in the M groups may be the sameas the R radicals attached to the silicon atoms or may be different.Preferably, the R radicals in the M groups are lower alkyl radicals of 1to 8 carbon atoms such as, methyl.

The radicals represented by R' may be any alkylene or arylene radicalsof up to 20 carbon atoms and more preferably of 1 to 10 carbon atomssuch as, mathylene, ethylene, various isomers of the phenylene radicalsof substituted propylene, phenylene radicals. In the preferredembodiment, R' is ethylene.

It should be noted that in a particular M group as defined above, ifthere are more than one R' radical the R' radical may be the same or maybe different.

In the case where the M is a polyether group, the R radical ispreferably butyl, an alkyl radical of 1 to 4 carbon atoms and morepreferably methyl. In addition, x is preferably 2 or 3 and n varies from4 to 100.

In the process for producing the silicone polymer fluids of the presentinvention, there is preferably hydrolyzed a mixture oforganohalosilanes. Thus, there is preferably used a mixture oforganohalosilanes in which mixture there is present 0 to 100 molepercent of organohalosilanes of the formula R₂ SiX.sub. 2, 0 to 100 molepercent of organohalosilanes of the formula R SiX.sub. 3, 0 to 10 molepercent of organohalosilanes of the formula SiX.sub. 4, and 0 to 5 molepercent of organohalosilanes of the formula R₃ SiX where in the aboveformulas R is as previously defined, and X represents halogen, mostpreferably, chlorine. To this general mixture of organohalosilanes thereis generally added 0 to 3.5 moles of water per mole of the mixture.

In the preferred reactant mixture of organohalosilanes there ispreferably present 75 to 95 mole percent of R₂ SiX.sub. 2organohalosilanes and 5 to 95 mole percent of R SiX.sub. 3organohalosilanes. In the most preferred reactant mixture of the presentinvention, there is utilized 85 weight percent based on the total weightof the organohalosilane reactant mixture of silanes of the formula R₂SiX.sub. 2 and 15 weight percent based on the weight of the totalreactant silane mixture of silanes of the formula R SiX.sub. 3. Thus, inthis preferred mixture of organohalosilanes there is preferably absentany substantial amount of silanes of the formula SiX₄ and R₃ SiX. In themost preferred embodiment of the present invention, a sufficient amountof water is added to the silanes so as to hydrolyze 25 mole percent ofthe chlorine atoms present on the organohalosilanes. More generally,there is preferably added sufficient water to hydrolyze 0 to 95 molepercent of the chlorine atoms present on the organohalosilanes and morepreferably 50 to 85 mole percent. In the case where the general reactantmixture is used, there is preferably added 0 to 3.5 moles of water permole of the organohalosilane mixture. The water is added slowly to thesilanes with agitation so as to obtain uniform mixing of the water inthe silanes and to obtain proper hydrolysis of the silanes. Although thereaction is exothermic, the evaporation and evolution of hydrogenchloride that is formed will normally reduce the temperature of thereaction in the range of 0 to 20° C and more preferably 0° to 10° C. Itis preferred to maintain the temperature of reaction during the additionof the water to the organohalosilanes below 20° C and more preferablybelow 10° C to prevent the organohalosilanes from being evaporated offfrom the reaction mixture.

The resulting hydrolyzate is a silicone polymer fluid with a certainnumber of chlorine atom substituents on the silicon atoms depending onthe amount of water that is added during the hydrolysis. A solution ofthis hydrolyzate is obtained by adding to the hydrolyzate one of thewell known water-immiscible organic solvents which is inert to thechlorine atoms in the hydrolyzate. Such a water-immiscible organicsolvent may be for instance, tolyene, xylene, benzene, octane, heptane,cyclohexane and etc. The resulting solution is then heated to atemperature in the area of 25° to 100° C and more preferably 25° -- 50°C, at which point the hydrolysis is substantially completed, and thehydrolyzate is in solution in the organic solvent.

At this point the chlorine atoms in the hydrolyzate may be substitutedby condensing the hydrolyzate with an alcohol. Examples of alcohols thatmay be used are ROH, ROR'OH, ROR'OR'OH, R(OC_(x) H_(2x))_(n) OH andR-N-R'OH where R and R' is as previously defined. The most preferredalcohol that may be used is 2-methoxy-2-ethoxy ethanol or higher. It hasbeen found that this alcohol results in a brake fluid which is verycompatible with presently available glycol based polyether brake fluids.The polyether substituent group and the amine substituent group may alsobe used to provide silicone hydraulic fluid of the present inventionwhich is highly compatible with glycol based polyether brake fluids. Inaddition, the amine substituent group is desirable in the siliconepolymer in that not only is the resulting silicone polymer moredesirably compatible with glycol based polyether fluids presently on themarket, but further and in addition, the presence of the amine groupbuffers the silicone fluid and results in the silicone fluid beingslightly basic which is desirable in a hydraulic fluid.

Preferably, there can be used the stoichiometric amount of the alcoholnecessary to react with the chlorine atoms. Preferably, to have completecondensation of the alcohol groups or substitution of the alcohol groupsfor the chlorine atoms, it is desired to use at least 10 weight percentexcess of the alcohol reactants disclosed above.

The alcohol is simply added to the solution of the silicone polymerfluid and the water-immiscible organic solvent with the necessary amountof agitation. Preferably, this reaction is carried out at a temperaturein the range of 25° to 100° C and more preferably in the temperaturerange of 25° to 50° C so that the hydrogen chloride that is formed mayeasily be evolved from the reaction mixture. This reaction takes placeanywhere from 30 minutes to 4 hours. It should be noted that thehydrolysis portion of the reaction usually takes place in 1 hour to 4hours depending on the amount of water that is added to theorganohalosilanes or the halosilanes. After the alcohol has been addedin the time period mentioned above and the reaction of condensationallowed to proceed in a temperature of 25° to 50° C, the reactionmixture is heated to the reflux temperature of the water-immiscibleorganic solvent which may be anywhere from 100° to 180° C, and then allthe solvent from the polymer product as well as any excess alcohol andany remaining hydrogen chloride is stripped off under vacuum. Inaddition to stripping off the water-immiscible organic solvent, theexcess alcohol and any remaining hydrogen chloride, it is also necessaryto strip off any cyclic siloxanes that have been formed in the processsince such cyclic siloxanes are undersirable in the silicone hydraulicfluid since their presence tends to decrease the compatibility of thefluid with other hydraulic fluids. This stripping procedure usuallytakes place from 1 to 4 hours. In addition, the silicone polymer fluidmay be heated to 185° C for a period of 5 to 10 minutes to remove offsome of the disiloxanes that may have been formed because too large aquantity of such disiloxanes is undesirable in the silicone polymerfluid of the present invention, particularly when the silicone polymerfluid is to be used as a brake fluid. The presence of such disiloxanesin the silicone polymer fluid of the present invention undesirablyaffects the boiling point of the fluid and results in volatiles beinggiven off at high temperatures. However, all the disiloxanes that areformed in accordance with the process of the present invention may beallowed to remain in the silicone fluid of the present invention withoutdetracting to a large extent from the advantages of the silicone polymerfluid of the present invention as a brake fluid. The resulting siliconepolymer fluid when cooled to room temperature has a viscosity of 2 to400 centistokes at 25° C and more preferably 7 to 20 centistokes at 25°C. Such a silicone fluid is a mixture of polymers having 2 to 2000silicon atoms in the polymer with the average polymer having 20 to 40silicon atoms.

In the most preferred embodiment of the above process there is used 85weight percent of organohalosilanes of the formula R₂ SiX₂ and 15 weightpercent based on the total weight of the organohalosilanes oforganohalosilanes of the formula RSiX₃. To this mixture which containsonly these types of organohalosilanes there is sufficiently addedsufficient water to hydrolyze 25 mole percent of the chlorine atomspresent. The other chlorine atoms on the silicones are substituted bythe alcohol moieties. If this most preferred hydrolysis procedure iscarried out then there will be obtained a silicone polymer fluidcontaining 20 to 48 weight percent of the MO or the hydrocarbonoxy-typeof groups based on the total weight of fluid. Such a silicone polymerfluid is extremely compatible with most silicone fluids useful as brakefluids and most non-silicone brake fluids and other types of hydraulicfluids.

In the more general embodiment of the present invention, there is addedsufficient water in the hydrolysis procedure so that there may bepresent in the final silicone fluid polymer 5 mole percent to 100 molepercent of hydrocarbonoxy type of groups, that is, MO groups, based onthe total molar amount of substituent groups present in the siliconepolymer.

It is, of course, obvious to the skilled worker in the art that thecritical phase of producing the novel silicone polymer fluid of thepresent invention is the amount of water that is used based on theamount of the organohalosilanes so that only the desired amount ofsiloxane bonds are formed. The chlorine atoms that remain on thehydrolyzed silicone polymer will, of course, be substituted by thealcohol moieties when the alcohol is added to the halogen containingsilicone polymer. Thus, the amount of water that is used in thehydrolysis not only controls the molecular weight of the final polymerand thus its viscosity but further, in addition, controls the amount ofhydrocarbonoxy groups that will be present on the silicone fluidpolymer.

In the preferred case where there is only present in theorganohalosilane mixture that is to be hydrolyzed R₂ SiX₂ silanes andRSiX₃ silanes, then it is preferred to use 0 to .93 moles of water permole of R₂ SiX₂ present in the organohalosilane mixture and 0 to 1.4moles of water per mole of RSiX₃ in the organohalosilane mixture. In themost preferred embodiment there is used 85 weight percent of the formulaR₂ SiX₂ and 15 weight percent of the organohalosilane of the formulaRSiX₃, where X stands for chlorine and there is added to this mixture0.8 moles of water per mole of the mixture so as to hydrolyze and formsiloxane bonds of 75 mole percent of the chlorine atoms on the silanes.The rest of the chlorine atoms are substituted by thehydrocarbonoxy-type of moieties. To produce the desired novel siliconepolymer fluid of the present case, it is necessary to use the specificamounts of water in the hydrolysis procedure as indicated above and suchamounts of water are critical to producing the silicone fluid polymersof the present case. It can be appreciated if too little water is addedthat the polymers that are formed will be of very low molecular weightthat is mostly disiloxanes which disiloxanes would not be as desirablein the fluid of the present invention for use as a hydraulic fluid.

The brake fluid of the present invention may also be made by analternative process which is not as economically advantageous as theprocess defined above. This alternative process comprising reacting analcohol selected from the class consisting of ROH, ROR'OH, ROR'OR'OH,RCOC_(x) H_(2x) )_(n) OH and ##STR8## where R, R' and x and n are aspreviously defined with a hydrogen organopolysiloxane of the formula

    R.sub. a H.sub.b SiO.sub.(4.sub.-a.sub.-b)/2               (1 )

In the presence of a platinum catalyst, where R has the meaning definedpreviously, a varies from 0.1 to 2.5, b varies from 0.1 to 2.5 and thesum of a + b varies from 2.01 to 3.00. The hydrogen polysiloxane isadded to a reaction chamber and then there is added a sufficient amountof toluene to the hydrogen polysiloxane or any other water-immiscibleorganic solvent so as to dissolve the hydrogen polysiloxane. Theresulting mixture is heated to a temperature in the range of 100° to150° C to remove any free water by toluene-water azeotrope. Once thesolution of hydrogen polysiloxane in the toluene is dried in accordancewith the azeotrope technique a trace of platinum catalyst is added tothe mixture. At this point, the alcohol in the proper amount, that is, 1mole of alcohol for each hydrogen atom in the hydrogen polysiloxane, isadded to the reaction pot slowly with agitation, preferably 10 molepercent excess of the alcohol may be used. The addition is exothermic sothat the temperature is controlled by the alcohol addition rate and isusually maintained in the range of 25° to 75° C. During the reaction,the SiH peak disappearance is followed by an infrared scan. Once theaddition of the alcohol to the hydrogen polysiloxane is completed thesolution is filtered through Fuller's earth to remove any precipitates.Then the solution is stripped to remove solvents and low boilingfractions to yield the desired polysiloxane which is within the scope ofthe general definition of the silicone fluid polymer of the presentinvention and can be thus used as a hydraulic fluid.

It should be noted that the hydraulic fluid prepared in accordance withthis alternative method does not contain any of the units that arederived by the use of the silane SiX₄ in the prior hydrolysis procedure.

The other types of units that are present in the novel silicone polymerfluid prepared in accordance with this alternative method are strictlywithin the defined limits of the average unit formula (1 ) above, whichaverage unit formula defines polymeric silicone fluids within the broadgeneric definition of the novel silicone polymeric fluids set forthpreviously.

Suitable catalysts for addition of the organohydrogenpolysiloxane to thealcohol are the various platinum and platinum compound catalysts knownin the art. These catalysts include elemental platinum in a finelydivided state which can be deposited on charcoal or alumina, as well asvarious platinum compounds such as chloroplatinic acid, the platinumhydrocarbon complexes of the type shown in U.S. Pat. Nos. 3,159,601 and3,159,662, as well as the platinum alcoholic complexes prepared fromchloroplatinic acid which are described and claimed in Lamoreaux's U.S.patent 3,220,972. Preferably, the platinum catalyst is added to theorganohydrogenpolysiloxane located in the reaction chamber to which isalso added a solvent and then the alcohol is slowly added to thereaction mixture at the reaction temperatures described above. Whetherelemental platinum or one of the platinum complex catalysts is used, thecatalyst is generally used in amounts sufficient to provide about 10⁻ ⁴to 10 ⁻ ⁶ moles of platinum per mole of the alcohol reactant. Asmentioned previously, the reaction is effected by addingorganohydrogenpolysiloxane to an inert solvent such inert solvent beingselected from the group consisting of benzene, toluene, xylene, mineralspirits and other inert solvents. The reaction mixture is preferablyheated to a temperature of 25° to 75° C before the addition of thealcohol reactant. The alcohol reactant is then added to the hydrogenpolysiloxane solvent mixture at an addition rate so as to maintain thereaction temperature indicated above. The reaction is allowed to proceedto completion in 4 to 15 hours and preferably in 5 to 8 hours. After thereaction period is over, a sample of the reaction mixture may be checkedby infrared analysis for SiH bonds to determine how far the reaction hasproceeded to completion. When at least 98% of the SiH organopolysiloxanehas been converted to the reaction product, reaction mixture may becooled and the reaction may be considered to have proceeded to asufficient extent for the conversion of the hydrogen polysiloxane to thedesired silicone polymeric fluid. The difficulty in this alternativeprocess is in preparing an organohydrogenpolysiloxane within the averageunit formula given above, that is, an organohydrogenpolysiloxane of theproper molecular weight, thus one having 2 to 2000 silicon atoms in thepolymer chain.

The polymeric and molecular configuration of the hydrogenpolysiloxane ofFormula (1) will in fact determine the structure and molecularconfiguration of the silicone hydraulic fluid produced from theorganohydrogenpolysiloxane since in the platinum catalyzed reactionthere is simply substituted a hydrocarbonoxy moiety for each hydrogenatom.

Preparation of the organohydrogenpolysiloxane of Formula (1) which cancontain both saturated and olefinically unsaturated hydrocarbon groupsmay be carried out by any of the procedures well known to those skilledin the art. Such polysiloxanes can be produced by following theprocedure involving the hydrolysis of one or morehydrocarbon-substituted chlorosilanes in which the substituents consistof saturated hydrocarbon groups. An excess of water is used in such ahydrolysis so as to obtain a crude hydrolyzate containing a mixture oflinear and cyclic polysiloxanes. To the hydrolyzate there is added acatalyst, preferably a basic or acid catalyst such as potassiumhydroxide, sodium hydroxide, toluene, sulfonic acid, etc. and thehydrolyzate mixture is heated to a temperature of about 150° C toproduce and recover by evaporation a product consisting C low molecularweight cyclic polysiloxanes. When the crude hydrolyzate mixture istreated with potassium hydroxide and heated to a temperature of at least100° C, the hydrolyzate is converted to a mixture of low boiling, lowmolecular weight cyclic polymers mixed with undersirable materials suchas monofunctional and trifunctional chlorosilane starting material. Thechlorosilanes that may be used are the ones indicated in the priorhydrolysis process with the exception that the silane SiX₄ is not used.

By heating the resulting mixture of cyclics to a temperature of 150° C,there is able to be collected a pure product of the low boiling, lowmolecular weight cyclic polymers free of any significant amount ofmonofunctional and trifunctional groups. If the hydrolysis andsubsequent polymerization is carried out properly, there is obtainedcyclic polysiloxanes comprising, for example, about 85% of thetetrasiloxane and 15% of the mixed trisiloxane and pentasiloxane. Theoverhead cyclic siloxanes contain substantially very little water and itis preferably that such cyclic siloxanes have less than 100 parts permillion of water. In the same way, there can be obtained alkyl hydrogencyclic siloxanes and other types of hydrocarbon substituted hydrogencyclic siloxanes. The cyclic siloxanes are then added in the desiredproportion in a reaction vessel so as to be subjected to anequilibration reaction to form the hydrogen polysiloxane of Formula (1).If desired and depending upon the type of compound that is to beproduced, 0.1 to 1.0 mole percent of methylvinylcyclicsiloxane may bemixed with the hydrogen methyl and dimethyl cyclicsiloxanes. In theequilibration reaction there may be used as a catalyst, any strong acid.There is preferably used in the present reaction, an acid such astoluene sulfonic acid or sulfuric acid and other types of strong acidswhich are well known in such polymerization reactions. There is furtheradded to the reaction mixture, the necessary amount of one or moremonofunctional compounds calculated to function as endblockers forlimiting the degree of polymerization and consequently the lengths andmolecular weights of the linear polysiloxane chains for stabilizing thepolymer.

In the present case, since it is desired that the final polymerpreferably not have more than 2,000 silicon atoms in the molecular chainand that the average polymer chain have about 20-40 silicon atoms, asufficient amount of the monofunctional endblocker units must be addedso as to properly limit the chain length of the resultinghydrogenpolysiloxane polymer. The functional compounds that may beemployed satisfactorily for controlling polymer growth include, amongothers, hexamethyldisiloxane, tetramethyldiethoxydisiloxane,dihydrogentetraethoxydisiloxane, divinyltetraethoxydisiloxane anddeca-methyltetrasiloxane. The equilibration reaction is carried out from2 to 4 hours until about 85% of the cyclic diorganosiloxanes have beenconverted to polymer end-stopped with monofunctional groups. When the85% conversion point has been reached, there are just as many polymersbeing converted to cyclic siloxanes as there are cyclic siloxanes beingconverted to the polymers. At that time the reaction mixture is cooledand there is added to the reaction mixture a neutralizing agent such asa bicarbonal so as to neutralize the acid catalyst that is present inthere. The cyclic diorganosiloxanes in the reaction mixture may then bedistilled off to leave the hydrogenpolysiloxane which is useful in thepresent invention. The above procedure can be used to produce branchchain hydrogenpolysiloxane as well as linear diorganopolysiloxanesdepending on the reactants that are used in the equilibration reaction.

An illustrative reaction to produce the hydrogenpolysiloxane within thescope of Formula (1) is to equilibrate octamethyltetrasiloxane andtetramethyltetrahydrogentetrasiloxane in the proper molar proportion inthe presence of 3% of acid-treated clay, such as 3% Fuller's earth andthen the reaction mixture is heated for 5 hours at 100° to 120° C toequilibrate the reaction mixture. There is also added to the reactionmixture, the proper amount of hydrogentetramethyldisiloxane. After 5hours of reaction time when approximately 85% of the tetramers have beenconverted to the polymer polysiloxane, the catalyst is neutralized witha weak base and the volatile cyclics are distilled off to leave asubstantially pure hydrogenpolysiloxane. The hydrogenpolysiloxane ofFormula (1) may then be reacted with one of the alcohols mentionedpreviously in accordance with the platinum catalyzed reaction discussedabove to produce the novel silicone hydraulic fluid polymers of thepresent invention having the formula,

    R.sub.a (MO).sub.b SiO.sub.(4.sub.-a.sub.-b)/2             (2)

where R, M, a and b and the sum of a and b is as previously defined inthe specification, that is, various from 0.1 to 2.5, b varies from 0.1to 2.5 and the sum of a + b varies from 2.01 to 3.0. Within this averageunit formula there is obtained a fluid silicone polymer within thepresent invention which contains ##STR9## units, R₂ SiO units, ##STR10##units and ##STR11## units and RSiO_(3/2) units and R₃ SiO_(1/2units)with the mole percent limits specified for the hydraulic fluids of thepresent case.

A silicone fluid polymer can be prepared by the use of this alternateprocedure, that is, the use of the hydrogenorganopolysiloxane, such thatthe fluid contains the units mentioned above which units are present ata concentration within the broad range of mole percents indicatedpreviously in the general definition of the fluids of the present case.Thus, by this alternative method, that is, through the use of anorganohydrogenpolysiloxane, there may be obtained a compound within thescope of Formula (2) which has the preferred combination andconcentration of ##STR12## units and R₂ SiO units, ##STR13## units,##STR14## units and RSiO_(3/2) units with some amounts of R₃SiO_(1/2units). Preferably, the second procedure is used when theaverage polymer chain desired in the final silicone hydraulic fluid ofthe present invention is to have 50 to 1,000 silicon atoms.

In addition, it is preferred to use the hydrolysis procedure of theorganohalosilanes which was first discussed in this specification inpreparing the novel silicon fluid of the present invention in that it isa less expensive procedure than the procedure utilizing thehydrogenpolysiloxane. For silicone polymers within the present inventionwhich are to have an average chain length of 2 to 40 silicon atoms, thefirst procedure is much preferred over the second alternative procedure.

In the case where the M substituent in the silicone fluid polymer of thepresent invention represents lower alkyl group and particularly methyl,it may be possible to prepare a silicone fluid within the scope of thepresent invention by forming methoxymethylcyclicsiloxanes in accordancewith the procedure indicated for forming theorganohydrogencyclicsiloxanes above and then equilibrating themethoxymethylcyclicsiloxanes to obtain a polymer in accordance with thediscussion above. The procedure for equilibrating such cyclic, alkoxyand particularly methoxyalkylcyclicsiloxanes would be the same as thatindicated for the production of the hydrogenorganopolysiloxane. Thus,after the equilibration reaction is over the final polymer would beformed and it would not be necessary to carry out further steps toproduce the desired alkoxy-substituted silicone polymer of the presentinvention. However, the difficulty with this alternative procedure whichis even less preferable than the procedure utilizing thehydrogenorganosiloxane, is that it is very difficult to obtainalkoxyalkylcyclicsiloxanes and it is also difficult to equilibrate suchcyclicsiloxanes without the use of special procedures. In addition, theequilibration reaction will proceed only with poor efficiency if thealkoxy-substitutent group on the cyclicsiloxane is of high molecularweight. Accordingly, the first process outlined in the specification isthe preferred process for producing the silicone hydraulic fluid of thepresent invention.

The novel silicone fluid of the present invention and particularly whenit is used as a hydraulic fluid or a brake fluid has many inherentproperties such that it does not require the addition of any additives.However, to enhance its properties there may be added various additivesin varying quantities. First, there may be added to the hydraulic fluidof the present invention at a concentration of 1 to 10% by weight ofsaid fluid a buffer compound having the formula, ##STR15## where R² isselected from the class of hydrogen, monovalent hydrocarbon radicals,halogenated monovalent hydrocarbon radicals and cyanoalkyl radicals, R³is selected from divalent hydrocarbon radicals, halogenated divalenthydrocarbon radicals of 2 to 10 carbon atoms. Preferably, R² is eitherhydrogen or a lower alkyl radical such as, methyl, ethyl, phenyl, etc.The radical R³ is preferably an arylene or alkylene radical of 2 to 10carbon atoms such as, methylene, propylene, phenylene, etc. Although thehydraulic fluid of the present invention may be used as a brake fluidwithout the above buffer compound as an additive, the above buffercompound may be added to cause the hydraulic fluid to be slightly basic.It is desirable that the hydraulic fluid of the present case be slightlybasic such that it absorbs free water at a faster rate. To thealternative at a concentration of 1 to 10% by weight of the fluid therecan be added an anhydride of a carboxylic acid which will also permitthe silicone fluid of the present invention to absorb water easily.

In addition to the above compounds there may be added variousantioxidants. An antioxidant compound additive to the hydraulic fluid ofthe present invention is not necessary but it may be added in aconcentration of 1 to 5% by weight of the fluid so as to enhance theantioxidant properties of the fluid of the present invention. Thus, inthe fluid of the present invention there may be antioxidant compoundsselected from the class consisting of ##STR16## and ##STR17## where R⁵is selected from the class consisting of hydrogen and monovalenthydrocarbon radicals and halogenated monovalent hydrocarbon radicals andis preferably hydrogen or lower alkyl radicals such as, methyl, ethyland etc., and R⁴ is selected from the class consisting of monovalenthydrocarbon radicals and halogenated monovalent hydrocarbon radicals andpreferably is lower alkyl such as, methyl, ethyl, isopropyl and etc. Aspointed out, although these additives may be added to the hydraulicfluid of the present invention particularly when it is going to be usedas a brake fluid, to enhance the antioxidant and buffer properties ofthe hydraulic fluid these additives are not necessary. The hydraulicfluid of the present invention has by itself the proper Ph value and inaddition has very good corrosion and antioxidant properties.Furthermore, a brake fluid within the scope of the present invention hasa viscosity of 100 to 150 centistokes at -40° C which makes it quitedesirable for use as a hydraulic fluid and a brake fluid in the articregions.

The hydraulic fluid of the present invention may tolerate 6% by weightof water and in fact may tolerate as much as 100% by weight of water ormore in some instances. The only undesirable effect of the addition ofwater above the 6% level, that is, 6% by weight of the silicone fluid ofthe present invention, is that this additional water may undesirablyaffect the boiling point of the resulting water-silicone fluid mixture.However, even at the high level concentration of 100% by weight of waterin the silicone fluid of the present invention, the water will notseparate out from the silicone fluid. In short, the silicone fluid ofthe present invention meets the highest requirements and specificationsfor hydraulic fluids.

The examples below are given for the purpose of illustrating the presentinvention and not intended to limit the scope of the claims or of theinvention defined here above in any way or manner.

EXAMPLE 1

There is added to a reaction flask 47.0 parts of (CH₃)₂ SiCl₂ and 7.3parts of CH₃ SiCl₃. To this mixture of methylchlorosilanes there is thenadded slowly with agitation 5.12 parts of water so as to hydrolyze 65mole percent of the chlorine atoms present in the organohalosilanes.During such addition of the water the reaction mixture is not heated andas a result of the hydrogen chloride vapors being given off in thehydrolysis, the reaction temperature is maintained at about 4° C. Theaddition of the water takes place in approximately 11/2 hours. After allthe water has been added, the hydrolyzate is heated to 30° C at whichpoint the hydrolysis is essentially complete. To the resultinghydrolyzate there is added 30 parts of toluene and the hydrolyzate isdissolved in the toluene with some agitation. After 15 minutes ofstirring the hydrolyzate into the toluene solution, the solution isheated to 50° C and there is added to it at this temperature 46.6 partsof 2-methoxy-2-ethoxy ethanol. The resulting ingredients are stirred for2 hours and the mixture is heated to a temperature of 50° C. At the endof that time, the resulting solution is heated to 158° C and maintainedat that temperature for 2 hours until all of the toluene, excess alcoholand cyclic siloxanes have been stripped off. At the end of that point,the solution is brought up to 185° C for about 5 minutes to remove someof the disiloxanes that have been formed which are deleterious to thedesirable properties of the fluid of the present invention.

The resulting fluid has a viscosity of 7 centistokes at 25° C and thereis present in said fluid 48 weight percent of 2-methoxy-2-ethoxyethylene groups based on the weight of the fluid. The infrared analysisdisclosed that the fluid contains the proper proportion of2-methoxy-2-ethoxy ethylene groups in the silicone polymer fluid andthat the fluid contains ##STR18## units, (CH₃)₂ SiO units, ##STR19##units, ##STR20## units and CH₃ SiO_(3/2) units, where Z is2-methoxy-2-ethoxyethylene.

EXAMPLE 2

Into a reaction chamber there is placed 46.0 parts of (CH₃)₂ SiCl₂, 8.0parts of CH₃ SiCl₃, and 0.2 parts of (CH₃)₃ SiCl. The resulting mixtureof organohalosilanes and halosilanes are mixed for 5 minutes and thereis added to them 5.12 parts of water which is sufficient water toreplace 70 mole percent of the chlorine atoms present on the silanes.The water is added slowly to the organohalosilanes over a period of 30minutes and the resulting evolution of hydrogen chloride gases maintainsthe reaction temperature at 9° C. After the addition of water has beencompleted, the mixture is agitated for 5 minutes and then it is heatedto a temperature of 30° C at which point there is added to the mixture30 parts of xylene to dissolve the hydrolyzate. After the hydrolyzatehas been dissolved in the xylene, the resulting solution is raised to55° C and there is added to the solution 46.6 parts of C₄ H₉ (OC₂ H₄)₁₅OH. This polyether is added to the solution of the hydrolyzate slowlywith agitation over a period of 1 hour and the reaction during that timeis maintained at 55° C. After all the polyether has been added thesolution is continually agitated for another 30 minutes and heated at55° C. Then the temperature of the solution is raised to 153° C andmaintained at that temperature for a period of 2 hours so as to stripoff all of the xylene, cyclicsiloxanes and excess alcohol from thesolution. After that time, then the remaining silicone fluid of thepresent case is heated at 185° C for about 5 minutes to remove a portionof disiloxanes that were formed. The residue that remains is the novelsilicone fluid of the present invention. Infrared analysis indicatesthat this silicone fluid contains 42% by weight of the fluid ofpolyether groups. The viscosity of this silicone fluid at 25° C is 25centistokes and it contains ##STR21## units, (CH₃)₂ SiO units, ##STR22##units, ##STR23## units, (CH₃)SiO.sub. 3/2 units, (ZO)₃ SiO_(1/2) units,(ZO)₂ SiO units, ZOSiO_(3/2) units, SiO₂ units and (CH₃)SiO_(1/2) units,where Z is C₄ H₉ (OC₂ H₄)₁₅.

The silicone fluid prepared in accordance with Example 1 is tested invarious brake fluid tests as to determine its suitability or superiorityas a brake fluid in terms of its evaluation in these tests.

One test that may be used is a dry equilibrium reflux boiling test whichis carried out by placing 60 millimeters of the hydraulic fluid in aflask and boiling under specified equilibrium conditions in a 100millimeter flask. The average temperature of the boiling fluid at theend of the reflux period is determined and corrected for variations ofbarometric pressure where necessary and the final value is itsequilibrium reflux boiling point. The hydraulic fluid of Example 1 whentested for its equilibrium reflux boiling point has a value of greaterthan 500° F.

A wet equilibrium reflux boiling test was carried out in the presentinvention wherein the hydraulic fluid of Example 1 was taken and therewas added 10% water by weight to it, and 0.1% three normal hydrochloricacid. Infrared spectra showed the appearance of a large OH bond, nowater band and a slight increase in polymer length and a silanolelement. When tested for its wet equilibrium boiling point it was foundthat the fluid of Example 1 with this large amount of water in it had awet equilibrium boiling point of 150° C. A typical glycol fluid withthis much amount of water in it had a wet equilibrium boiling point of105° C, thus, indicating the superiority of the silicone fluid of thepresent invention in maintaining its high boiling point and beingcompatible with a large amount of water while still maintaining a hightemperature stability and a high boiling point. The water is preventedfrom being boiled out of the silicone fluid and thus forming a vaporlock in hydraulic lines as is possible with a glycol based fluid. A wetequlibrium reflux boiling point determination was obtained by firsthumidifying 10 mole of the fluid of Example 1 for three days at 80%relative humidity along with 100 millimeters of SAE compatible fluidwherein at the end of the three days the compatibility fluid hadabsorbed 3% by weight water and the fluid of Example 1 absorbed 0.3% byweight of water. The humidified fluid of Example 1 when tested for itswet equilibrium reflux point in the same way as for the determination ofthe dry equilibrium reflux boiling point had a wet equilibrium refluxboiling point of greater than 320° F.

For the flash point determination, the test is to take a test dish whichis filled to a specified level with the hydraulic fluid of the presentcase. The fluid temperature is increased rapidly and then at a slowerrate as the flash point is approached. At specified intervals, a smalltest flame is passed across the cup. The lowest temperature at whichapplication of the test flame causes the vapors above the fluid surfaceto ignite is the flash point. The hydraulic fluid of Example 1 has aflash point of at least 350° F.

The kinematic viscosity test is a determination of the measure of thetime necessary for a mixed volume of the hydraulic fluid to flow througha calibrated glass capillary viscometer under an accurately reproducablehead and a closely controlled temperature. The kinematic viscosity isthen calculated from the measure of flow time in the calibrationconstant viscometer. At -40° C the hydraulic fluid of Example 1 had aviscosity of 100 centistokes and at 212° F the hydraulic fluid ofExample 1 had a viscosity of 1.8 centistokes.

In the pH value determination a quantity of the hydraulic fluid isdiluted in an equal volume of methanol water solution. The pH of theresulting solution is measured with a prescribed pH meter assembly at23° C. Without the buffer compound additive disclosed in the presentspecification, the hydraulic fluid of Example 1 has a pH of 6.8. With 1%by weight of the hydraulic fluid of Example 1 of a buffer compoundhaving the formula ##STR24## the resulting hydraulic fluid has a pH of8.1. The brake fluid stability comprises a high temperature stabilityand a chemical stability test. In the case of the high temperaturestability test, a 60 millimeter sample of the brake fluid is heated toan appropriate holding temperature and then the brake fluid ismaintained at a holding temperature for 120 ± 5 minutes. Then for thenext 5 ± 2 minutes the fluid is heated to an equilibrium reflux rate of1 to 2 drops and the temperature is taken. The hydraulic fluid ofExample 1 was able to be maintained at that reflux rate without any dropin temperature.

In the case of a chemical stability test, 30 ± 1 millimeters of thehydraulic fluid is mixed with 30 ± 1 millimeters of SAE-1 compatibilityfluid in the boiling flask. First, the initial equilibrium refluxboiling point of the mixture is determined by applying heat to the flaskso that the fluid is refluxed for 10 ± 2 minutes at a rate in excess ofone drop per second. Then over the next 15 ± 1 minutes the reflux rateis adjusted and maintained to one to two drops per second. This rate ismaintained for an additional two minutes and the average value isrecorded as the final equilibrium reflux boiling point. The change inthe reflux boiling point during the test is measured. In this case therewas no change in the reflux boiling point during the test.

The hydraulic fluid of Example 1 when tested according to these testssuffered a negligible drop in temperature.

The corrosion test comprises polishing, cleaning and weighing 6specified metal corrosion test strips and assemblying them as prescribedin the standards. This assembly is placed on a standard rubber wheelcylinder cup in the corrosion jar and immersed in the brake fluid,capped and placed in an oven at 100° C for 120 hours. Upon removing andcooling the jar, the strips in the fluid cup are examined and tested.The metal test strips are observed to note whether there are anycrystalline deposits which form and adhere to the glass jar walls or thesurface of the metal strips and whether there is sedimentation in thefluid water mixture. The metal strips are weighted for weight loss andother determinations are made with respect to them. Thus, in the resultsof this test in terms of the metal weight loss, the steel strip suffereda loss of 0.15 milligrams/cm², the aluminum strip suffered a loss of 0.1milligrams/cm², the brass strip suffered a loss of 0.2 milligrams/cm²,the copper strip suffered a loss of 0.2 milligrams/cm², the iron stripsuffered no loss, and the plated steel strip suffered no loss. There wasno gelling of the fluid at the high temperature and no gelling of thefluid at the low temperature of 23 ± 5° C. There were no deposits in thefluid and the sediment that was weighted was less than 0.1 weightpercent of the fluid. The pH of the fluid after the test was between 7to 11.

The next test is the effect on rubber where four selected styrenebutadiene rubber cups are measured and their hardness determined. Thistest is known as the Rubber Swell Test J-1703. In this test the cups areplaced two to a jar and are immersed in the hydraulic fluid ofExample 1. One jar is heated for 120 hours at 70° C and the other for 70hours at 120° C. After this, the cups are removed, washed and examinedfor disintegration. They are remeasured and their hardness redetermined.In this test the cups after being immersed in the hydraulic fluid of thepresent invention in accordance with the above test had a hardness of 15when measured at the end of the test. In addition, the swell wasmeasured to be 1.2 millimeters. This test was also run with the Neoprenerubber cups and the swell was found to be with Neoprene rubber cups tobe 4% by volume. In addition, the test was carried out withethylene-propylene rubber cups where the swell was found to be 2%. Inthese other latter tests the rubber after the test is tested and foundto have a hardness of 15 and 16, respectively. All these values forswell are sufficient to pass the requirements for brake fluids.

In the fluid appearance at low temperature test the test comprisestaking the hydraulic fluid of Example 1 and lowering it to expectedminimum exposure temperatures such as -40° C and then the fluid is thenobserved for clarity, gellation, sedimentation, excessive viscosity ofthixotropity. The hydraulic fluid of Example 1 with 3.5% of water in ithas no crystallization, cloudiness sedimentation when taken to this lowtemperature -40° C, and further upon reversion of the sample bottle inwhich the test is carried out, the time required for the air bubble totravel to the top of the fluid is less than 10 seconds.

In the water tolerance test the hydraulic fluid is diluted withsufficient water so that there is 3.5% by water in the fluid and it isstored at low temperatures of -40° to -50° C for 24 hours. The coldwater wet fluid is first examined for clarity, stratification,sedimentation and placed in an oven at 60° C for 24 hours. Then it isremoved and again examined for stratification and sedimentation. Thehydraulic fluid of Example 1 when subjected to this test, that is, afterit is kept at -40° to -50° C for 24 hours, was clear and there was nostratification or sedimentation. Further, even after being placed in anoven at 60° C for 24 hours, there is again no stratification and nosedimentation.

The other important test is the compatibility test in which a sample ofthe hydraulic fluid of Example 1 is mixed with an equal volume of SAEcompatibility fluid, then tested in the same way as the last mentionedtest which is the water tolerance test. When the hydraulic fluid ofExample 1 was mixed with equal volume of SAE compatibility fluid whichis a glycol based brake fluid and as observed after the necessary timeat the low temperature -40° to 50° C, and also after the necessary time,that is, 24 hours at 60° C, the fluid is found not to have stratifiedand not to have any sedimentation, and also to be perfectly clear inboth cases.

The hydraulic fluid of Example 1 was also tested in several other testswhich will not be mentioned here in detail such as, the resistance tooxidation test, the stroking properties test, the evaporation test whichtests are usually specified for brake fluids and it is found that thehydraulic brake fluid of Example 1 performs in a superior manner inthese tests, as compared to the glycol based polyether fluids. The teststhat have been discussed in detail above are the particular tests forbrake fluids which show the advantages and superior properties of thehydraulic fluid of Example 1 and more generally the hydraulic fluid ofthe present invention as a brake fluid.

The above examples were given for the purpose of illustrating theadvantages of the hydraulic fluid mixtures of the present invention overconventional hydraulic fluids and more particularly over conventionalbrake fluids. It is not intended in any way or manner by these examplesto limit the application of the hydraulic silicone fluid mixturesdefined in this application solely for use as a brake fluid in anautomotive system or as a brake fluid in any other type of vehiclesystem. Generally, as has been stated previously, the hydraulic siliconefluid mixture as defined in the present specification, may be used inany type of hydraulic system including any type of hydraulic brakesystem of any type of vehicle.

I claim:
 1. A process for producing a novel silicone fluid polymeruseful as a hydraulic fluid consisting essentially of (a) adding up to3.5 moles of water per mole of a mixture of silanes having therein 75 to95 mole percent of R₂ SiX₂, 5 to 25 mole percent of RSiX₃, and traceamounts of silanes selected from the class consisting of SiX₄ and R₃ SiXwhere there is added sufficient water to replace 50 to 85 mole percentof the X atoms present in the silanes, X is selected from halogen, R isselected from the class consisting of monovalent hydrocarbon radicals,halogenated monovalent hydrocarbon radicals and cyanoalkyl radicals andwhich reaction is carried out at a temperature of 9° to 20° C; (b)adding with agitation to the hydrolyzate up to 30 parts of awater-immiscible organic solvent to form a solution; (c) heating theresulting solution to 25°- 100° C; (d) agitating into the solution 0.15to 3.0 moles of an alcohol selected from the class consisting of ROH,ROR' OH, and ROR'OR'OH, and R(OC_(x) H_(2x))_(n) --OH, where R is aspreviously defined, R' is selected from divalent hydrocarbon radicalsand halogenated divalent hydrocarbon radicals, x varies from 2 to 4 andn varies from 4 to 100; (e) heating and resulting mixture to the refluxtemperature of the solvent to strip off all solvent, cyclic siloxanesand free alcohol; and (f) cooling the resulting silicone polymer fluidto room temperature.
 2. The process of claim 1 wherein thewater-immiscible organic solvent is selected from the class consistingof xylene and toluene.
 3. The process of claim 1 wherein the heating instep (e) is in the temperature range of 100° C to 185° C.
 4. The processof claim 1 wherein the final silicone polymer fluid has a viscosity inthe range of 2 to 4 centistokes at 25° C.